1/4 FLORIDA GEOLOGICAL SURVEY SIXTH ANNUAL REPORT. 



absence of certain species, regardless of their relative abundance 

 and structural adaptations. 



In a certain neighborhood a certain plant may be common and 

 apparently confined to a particular geological fonnation or type of 

 soil, so as to lead to the belief that it is a good indicator of that 

 type of soil* ; but if a few specimens of the same plant are after- 

 wards found on a very difTerent soil in another part of the country 

 that hypothesis is usually abandoned. But again the plant on the 

 other soil, at first supposed to be the same species, may upon closer 

 investigation be found to be a little different, and thus the original 

 correlation may be re-established. In such cases everything de- 

 pends on correct identification, an art in which very few botanists 

 .are proficient in this day and time. 



A much better way of correlating vegetation with soil is to de- 

 termine (first the relative abundance of the different species in a 

 given area, and then group together all those that have some char- 

 acter in common, such as trees, vines, evergreens, grasses, or plants 

 belonging to some particular family, and see what proportion they 

 make of the total. Some significant correlations can then often be 

 made between these statistics and certain soil characters, such as 

 texture or moisture or the percentage of some particular element 

 or combination of elements. This kind of work could be carried on 

 after a fashion by a botanist in a strange land where he did not know 

 the name of a single plant; though of course it would be desirable 

 to know the familv to which each one belonsfed. 



The usual way of studying the plant population of a state, 

 county, or other area, is merelv to make a list of the species of 

 plants, noting their local distribution, habitats, etc.; which is a 

 study of the flora rather than of the 7'cc/cfation. The flora of Flor- 

 ida is now pretty well known, but this knowledge has been of com- 

 paratively little use to geographers. The inadequacv of qualitative 

 studies may be illustrated by some analogies from other lines of 

 investigation. A census report does not simply state that the popu- 

 lation of a certain city, county or .state is composed of natives and 

 of immigrants from England. France, Germany, etc., but tells exact- 



*For references to several studies of this kind see Ann. N. Y. Acad. Sci. 

 17:8-9 Cfootnote), 1906. See also Hilgard. Tenth Census U. S. 5:68 — 69, 76, 229. 

 1884: Soils. 487-526. 1906. 



